DD_Raptor Posted June 12, 2016 Report Share Posted June 12, 2016 Hi all new to the forums and have a question I am sure has been addressed numerous times. I have never owned a weapon of any kind and only ever really fired one was back in Basic Training. I just never felt the need until lately. Anyway, I bought a DPMS LR-308 new at a pawn shop. I had the guy build me little better weapon. He suggested I put on a Troy ~13 3/4 rail, change to a Magpul ACS stock, said something about a gas block change( I have to confer with him to make sure) and added a Truglo three color Dot site and a Sight Mark Green light laser/flashlight. Now the problem I am having is feeding/cycling (BCG oiled wet) as well as last round the BCG doesn't lock open. I have taken it apart cleaned lubed and tried again numerous times with the same result. I realize having only ~ 75 rounds through it that could be part of the problem, since their chambers a tight and rough from what I gather. That party as aggravating as it is, is not my main concern. That would be the bolt locking open on last round. With a mag in place I can lock it open so that seems ok. I have taken apart the buffer assy. and measured the buffer, buffer spring and magpuls buffer tube depth as well as the buffer weight. They are as follows. Buffer Length - 2 1/2" Weight - 3.8 oz Spring Length 11 1/4" Coils ~ 27 - 29 depending on how you count LOL Magpul Buffer tube depth - 7" best I can tell. Any ideas/tips Quote Link to comment Share on other sites More sharing options...
blue109 Posted June 12, 2016 Report Share Posted June 12, 2016 Did you fire it before the modifications? Quote Link to comment Share on other sites More sharing options...
shepp Posted June 12, 2016 Report Share Posted June 12, 2016 Welcome to the forum, some one will come alone and beable to answer your questions. I think one other thing we might need is what kinda mags and have you tried others (but I maybe wrong). Quote Link to comment Share on other sites More sharing options...
DD_Raptor Posted June 12, 2016 Author Report Share Posted June 12, 2016 (edited) @blue109 No I did not. It was new and the dude at the Pawn shop did all the mods before I took it home. Edited June 12, 2016 by DD_Raptor Quote Link to comment Share on other sites More sharing options...
DD_Raptor Posted June 12, 2016 Author Report Share Posted June 12, 2016 26 minutes ago, shepp said: Welcome to the forum, some one will come alone and beable to answer your questions. I think one other thing we might need is what kinda mags and have you tried others (but I maybe wrong). I have one DPMS mag and one Magpul, both do the same thing. Quote Link to comment Share on other sites More sharing options...
blue109 Posted June 12, 2016 Report Share Posted June 12, 2016 Looks like the buffer stuff is right, and doubt both mags are bad. I'm assuming it's carbine length gas so the system should have plenty of punch in any case. I'd look at that gas block. If he misaligned it it may be choking off the gas port. Are you able to remove the rail to expose and examine the gas system? Also, pull the upper and slide the carrier in and out by hand. Make sure it moves nice and smooth, and that the gas key isn't hitting or binding on the gas tube when it closes. One thing I do with any new 308 build is start with one round in the mag. Do this a few times to make sure it locks back. Once you get that situated, put two or three rounds in. Its easier to troubleshoot one problem at a time. Quote Link to comment Share on other sites More sharing options...
DD_Raptor Posted June 12, 2016 Author Report Share Posted June 12, 2016 (edited) Thanks for the reply! In answer to your questions... 1) Are you able to remove the rail to expose and examine the gas system? - I have never actually done it but I assume it's only some screws holding it on. Then what do I look for? 2) Also, pull the upper and slide the carrier in and out by hand. Make sure it moves nice and smooth, and that the gas key isn't hitting or binding on the gas tube when it closes. - I looked at this earlier today and I couldn't tell one way or the other. Looks clean to me, but I will inspect closer. 3) One thing I do with any new 308 build is start with one round in the mag. Do this a few times to make sure it locks back. Once you get that situated, put two or three rounds in. Its easier to troubleshoot one problem at a time. - I have been fighting this thing for ~ 3 months off and on when I can, probably ~ 5 outings at most. Most rounds I have ever had in a clip is probably 5. I usually do 3 cause of the problems. At first did try 1 round at a time with the same results, but haven't tried since. I am just trying to gat as many rounds through it as possible right now. Unfortunately I will not be able to try it out again with one round for a couple of weeks. So what would you suspect if one round doesn't lock it back? Edited June 12, 2016 by DD_Raptor Quote Link to comment Share on other sites More sharing options...
shepp Posted June 12, 2016 Report Share Posted June 12, 2016 I assume you can manually lock it back? Quote Link to comment Share on other sites More sharing options...
DD_Raptor Posted June 12, 2016 Author Report Share Posted June 12, 2016 19 minutes ago, shepp said: I assume you can manually lock it back? Thanks for the reply... Yes, with a mag in place, I can manually lock it back and then it travels a bit more if I pull the charge handle after lock. That's without pushing the thingy in the side to lock it, if that's what you mean. Quote Link to comment Share on other sites More sharing options...
shepp Posted June 12, 2016 Report Share Posted June 12, 2016 18 minutes ago, DD_Raptor said: Thanks for the reply... Yes, with a mag in place, I can manually lock it back and then it travels a bit more if I pull the charge handle after lock. That's without pushing the thingy in the side to lock it, if that's what you mean. Yup Quote Link to comment Share on other sites More sharing options...
Wolfgang1952 Posted June 12, 2016 Report Share Posted June 12, 2016 What kind of gas block was on it? Was it an clamp on or had set screws? Like others have said your gas block may not be levial – inline with the gas port. I don’t see anything wrong other it is not getting enough gas to work the BCG properly. Quote Link to comment Share on other sites More sharing options...
DD_Raptor Posted June 13, 2016 Author Report Share Posted June 13, 2016 (edited) 11 minutes ago, Wolfgang1952 said: What kind of gas block was on it? Was it an clamp on or had set screws? Like others have said your gas block may not be levial – inline with the gas port. I don’t see anything wrong other it is not getting enough gas to work the BCG properly. I wish I knew what gas block it had on it, if he even changed it. I'll have to ask him tomorrow when their open. I do plan on talking to DPMS tomorrow about it via phone. Just one more thing now that I though of it, AMMO, I am using (on the cheap) some Perfecta 147g FMJ and some like 150g Winchester rounds Neither make any difference. Edited June 13, 2016 by DD_Raptor Quote Link to comment Share on other sites More sharing options...
Wolfgang1952 Posted June 13, 2016 Report Share Posted June 13, 2016 Shouldn’t be the ammo. I run the cheapest 308 I can find, but I stay away from steal case. Quote Link to comment Share on other sites More sharing options...
blue109 Posted June 13, 2016 Report Share Posted June 13, 2016 Any factory brass cased ammo should run fine in that gun. Most of the time people consider them over gassed. With that said, I usually have some known high quality hard hitting ammo on hand for initial function check. Some heavy (168-175gr) federal gold metal match is a good choice. Just to remove one step from the troubleshooting process. If the carrier is sliding by hand, and you don't feel a little "bump" right before it closes to indicate the gas tube is hitting the key, than you are probably fine. It would be noticable. I've never had that hanguard, but it's probably not too tough to remove. There's most likely a YouTube video out there about it. I'd say pull it off and snap a few pics. Its most likely that, or the magazine. There's a chance that the factory put a standard AR15 bolt catch in there. We've seen it happen here. Could even be an over-gas situation causing the bolt to outrun the catch. Welcome to the 308ar jungle lol. We'll get you sorted out. Quote Link to comment Share on other sites More sharing options...
DD_Raptor Posted June 13, 2016 Author Report Share Posted June 13, 2016 Appreciate it peeps and will let you know what I find after closer inspection. I want AMMO if a part he install is wrong or bad and make him fix it. Make sense? Quote Link to comment Share on other sites More sharing options...
survivalshop Posted June 13, 2016 Report Share Posted June 13, 2016 Factory DPMS LR 308 , will probably have the correct Bolt Stop ,if it truly is a new Factory Rifle , as said and not molested , you never know . The Troy Rails I have had , just clamp on the Troy type Barrel Nut or have screws that bolt HG to the Barrel Nut . Should be easy enough to undo the Bolts or screws & slide the HG off the Barrel Nut , as said instructions are easy enough to get from the Troy web sight . From what I have been reading on this thread , I would see if the Gas Block was changed & is miss aligned also . I doubt its over gassed , but under gassed is possible . Do you know if its a DPMS Barrel ? Did the Rifle come Boxed in a DPMS box ? What I'm getting at is, we have seen some Barrel Manufacturers that haven't a clue on Gas Port sizes for a 308 AR & if this barrel has been changed or if its someones build , there could be issues. Another thing you can check , when hand cycling the BCG with out a magazine , on the recoil cycle ( pulling it back ) , do you feel it slow down or feel resistance, after the Hammer has already been cocked ? Some times the Hammer can contact the Disconnector in the Trigger assembly , you will see a mark on the top, front area of the Disconnector . Is the Receiver Extension ( Buffer tube ) correctly Threaded in to the Lower Receiver & the Buffer Retaining Pin set correctly ? Early DPMS rifles had some rough & tight chambers & Polishing them with Flitz Metal Polish & a Bore mop on a Battery operated drill will help . The rough or tight Chamber can slow down the Extraction of the fired case enough to issues with Timing . Just need more info , you have to do some detective work , to get the proper answers . I know your having fun now ! Quote Link to comment Share on other sites More sharing options...
DD_Raptor Posted June 13, 2016 Author Report Share Posted June 13, 2016 10 hours ago, survivalshop said: Factory DPMS LR 308 , will probably have the correct Bolt Stop ,if it truly is a new Factory Rifle , as said and not molested , you never know . Your right you never know, but my son-in-law really likes him and says he's really good with guns.. But... The Troy Rails I have had , just clamp on the Troy type Barrel Nut or have screws that bolt HG to the Barrel Nut . Should be easy enough to undo the Bolts or screws & slide the HG off the Barrel Nut , as said instructions are easy enough to get from the Troy web sight . Will do am planning that shortly. From what I have been reading on this thread , I would see if the Gas Block was changed & is miss aligned also . I doubt its over gassed , but under gassed is possible . Pawn shop dude said it is a new low profile block because of the Troy rail. Do you know if its a DPMS Barrel ? Did the Rifle come Boxed in a DPMS box ? What I'm getting at is, we have seen some Barrel Manufacturers that haven't a clue on Gas Port sizes for a 308 AR & if this barrel has been changed or if its someones build , there could be issues. I talked to the Pawn shop dude and he assured me it was a new gun (under warranty) and the barrel is DPMS. ->The rifle was setting in the display but when I picked it up I did get the original box and the numbers match Another thing you can check , when hand cycling the BCG with out a magazine , on the recoil cycle ( pulling it back ) , do you feel it slow down or feel resistance, after the Hammer has already been cocked ? Some times the Hammer can contact the Disconnector in the Trigger assembly , you will see a mark on the top, front area of the Disconnector . Will check this out. Is the Receiver Extension ( Buffer tube ) correctly Threaded in to the Lower Receiver & the Buffer Retaining Pin set correctly ? Pawn shop man mentioned this also but I have no clue on how to check outside of a search. I may take it in to him for this. Early DPMS rifles had some rough & tight chambers & Polishing them with Flitz Metal Polish & a Bore mop on a Battery operated drill will help . The rough or tight Chamber can slow down the Extraction of the fired case enough to issues with Timing . May need to look into this by pawn shop man... Just need more info , you have to do some detective work , to get the proper answers . I know your having fun now ! Oh yes I am having more fun than a barrel of monkeys. Thanks for you reply! Quote Link to comment Share on other sites More sharing options...
DD_Raptor Posted June 13, 2016 Author Report Share Posted June 13, 2016 And now some pictures. Hopes this helps you guys out. The barrel had DPMS 7.62 x 51 1-10 stamped on it. The gas block was tight no signs of leakage. The only marking I could see is an A. I am not sure on how to check the alignment though. Quote Link to comment Share on other sites More sharing options...
392heminut Posted June 13, 2016 Report Share Posted June 13, 2016 That gas tube looks too short! We've had that problem before with builds that used an Armalite spec gas block position on the barrel, Armalite's gas tubes are just a bit longer than the DPMS tubes, which are stock AR-15 length.. If this is a DPMS factory build I can't understand why the tube would be short though? Too short of a gas tube will cause the problems you are experiencing though. If you look in the 3rd pic posted, the gas tube should extend back to about the middle of the cutout in your upper receiver. Quote Link to comment Share on other sites More sharing options...
Fletch Posted June 13, 2016 Report Share Posted June 13, 2016 Have you checked to make sure the gas rings on the bolt are staggered properly? Quote Link to comment Share on other sites More sharing options...
DD_Raptor Posted June 13, 2016 Author Report Share Posted June 13, 2016 I have to find out about that length from DPMS. I have made sure the gas rings were staggered. Thanks for your replies. Quote Link to comment Share on other sites More sharing options...
survivalshop Posted June 13, 2016 Report Share Posted June 13, 2016 Proper orientation of Gas Tube , as 392Heminut said , yours is short & will cause issues . These are actual lengths of Gas Tubes, you need to remove the Gas Tube & compare & get the proper size . Looks like something is not right about the size differences, Looks like you only need about a 3/8" or so , need to take measurements. I would check to make sure your Barrel is seated all the way , Barrel Extension Flange seated up against the Upper Receiver . Looks like its an Areo Gas Block . DPMS Gas Tube/AR 15/16 Pistol 6-5/8 Carbine 9-3/4 Mid-Length 11-3/4 Rifle 15-1/4 Armalite lengths, Rifle ( 308 ) ----- 15.5 " Carbine ( 308 )--12 1/16" super SASS Carbine ( 308 )--11" Super SASS< Rife (308 ) ? Mid ,( 223 )------------------ 11 3/4" Carbine ( 223) --------------- 9 3/4 " Rifle ( 223 ) ------------------- 15 3/16" National Match--------------- ? Quote Link to comment Share on other sites More sharing options...
mrmackc Posted June 13, 2016 Report Share Posted June 13, 2016 Are we now talking about apples and oranges being the same? APPLES? DPMS Gas Tube/AR 15/16 Pistol 6-5/8 Carbine 9-3/4 Mid-Length 11-3/4 Rifle 15-1/4 ORANGES? Armalite lengths, Rifle ( 308 ) ----- 15.5 " Carbine ( 308 )--12 1/16" super SASS Carbine ( 308 )--11" Super SASS< Rife (308 ) ? Mid ,( 223 )------------------ 11 3/4" Carbine ( 223) --------------- 9 3/4 " Rifle ( 223 ) ------------------- 15 3/16" National Match--------------- ? Quote Link to comment Share on other sites More sharing options...
DD_Raptor Posted June 13, 2016 Author Report Share Posted June 13, 2016 I see what you mean now survival shop. It does appear short by that photo you posted. I am not sure what to compare it to the apple or the orange. But I will take it apart and measure it best I can. I did speak to a DPMS rep and he pretty much didn't want to say anything since it had been modified a bit. SO that was of no help. Quote Link to comment Share on other sites More sharing options...
mrmackc Posted June 13, 2016 Report Share Posted June 13, 2016 (edited) DPMS is like Ford, if you hot rod your F150 your warranty is VOID Edited June 13, 2016 by mrmackc Quote Link to comment Share on other sites More sharing options...
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